Thanks, Mark. Out of interest, do you prepare Dimezone S in propylene glycol so as to make it easier to measure such a small amount, or do you just use 0.001 precision scales, which would really mean 0.0001 precision, I suppose? I can see how making the concentrate can be a better proposition, overall, for the consistency of measurement.

I do both.

I usually mix 2 litres worth of concentrate, and that's enough that I can measure Dimezone S directly using my .001 resolution scale. But for small tests, I use Dimezone S mixed with propylene glycol in a 2% solution like this: